German Patent Application DE 103 46 964 A1 describes a dishwasher whose walls are provided with an insulation having a variable thermal conductivity. This makes it possible to adjust the thermal insulation layer during the dishwashing operation in such a way that it has a low thermal conductivity and the thermal energy is retained in the washing chamber. On the other hand, during the drying process, the thermal conductivity can be increased so that an inner wall is cooled by removal of thermal energy to then accelerate the removal of moisture by condensation. In order to change the thermal conductivity, hydrogen in a metal hydride lattice is released, the hydrogen then changing the thermal conductivity. The use of such a metal hydride lattice in a thermal insulation layer involves a relatively high degree of complexity, because electrical heating means must be provided for the operation of the thermal insulation layer.
Other commercial dishwashers have a washing chamber surrounded by walls which are thermally insulated by an insulation layer. It is possible, for example, to provide an insulation layer of bitumen. However, the thermal conductivity of such insulation layers cannot be changed. Therefore, the thermal conductivity remains constant, irrespectively of whether the heat should be retained in the washing chamber during the dishwashing operation, or whether, during the drying operation, the heat should be removed from the washing chamber as efficiently as possible so as to cool an inner wall and accelerate the condensation process.